Enhancement of the coordinating flexibility in a Schiff-Mannich combo ligand: forced generation of a new NiII-Ophenoxo-LnIII-Oalkoxo-LnIII array (Ln = Gd, Tb, Dy and Ho)

3d-4f coordination complexes derived from appropriately designed ligand backbones offer great perspectives to construct functional magnetic materials. Here we have reported a ligand design strategy by introducing flexible ethanol amine arms in a conventional salen type ligand by Schiff base and Mannich reaction and shown how this Schiff-Mannich combo ligand approach afforded a series of Ni(II)LnIII2 (Ln = Gd, Tb, Dy and Ho) complexes. We have reacted the ligand with Ni-II to generate a metalloligand and by means of secondary assembly of this metalloligand with Ln(III) salts, the above mentioned Ni(II)LnIII2 series have been realized. As far as our knowledge goes, this Ni-II-Ln(III)-Ln(III) topology has not been reported in the literature to date. In-depth structural analysis of the ligand and the complexes has been carried out and this structural understanding will enable us to correlate the structure-property relationship in a better way. Magnetic studies indicated that the Dy-III analogue exhibits the slow relaxation of magnetization behavior under 800 Oe external dc field with energy barrier 2.94 K.

Automated summary

The article introduces a ligand design strategy with flexible ethanol amine arms, successfully preparing a series of Ni(II)LnIII2 complexes, exploring their structure-property relationships, and discovering a novel Ni-II-Ln(III)-Ln(III) topology.